Molecular cloning of one splicing form of human M6b cDNA

X-linked, early onset Pelizaeus-Merzbacher disease (PMD) and part of X-linked spastic paraplegia are caused by mutation of proteolipid protein. M6b (U45955) partially cloned by Olinsky was considered as a member of PLP gene family. One novel fragment about 300bp partially overlapped but differed in 5'part with U45955 was obtained by nested PCR. Assembly of the novel sequence with U45955 make a 1.642kb cDNA sequence with an open reading frame encoding 265 amino acids, which was verified by sequence of PCR products from brain cDNA library. The cDNA (termed M6ba) and its deduced peptide sequence showed significant similarity to murine M6b gene and protein (91.2% and 93.4% respecitvely). Northern blot, PCR amplification in cDNA library and EST analysis indicated that human M6b gene has at least three splicing forms. M6ba also showed significant similarity to PLP gene, they encode strongly hydrophobic protein and all their hydrophobic region are highly conserved. Gene structure analysis showed that the coding region of M6ba was composed of seven exons.